Ilum is considered to be a holy planet to the Jedi. For thousands of years, aspiring Jedi have tested their mettle on this distant planet in the crystal caves, have journeying the caves as a final part of their trials to find their lightsaber crystals. However, illusions will come to any who enter in an attempt to surround young Jedi with fear and force them to run in terror. Only when you overcome these illusions will you find what you seek. Only then will you truly be a Jedi.